In forming multi-level integrated circuit devices, a major portion of the manufacturing cycle involves chemical vapor deposition (CVD), for example plasma enhanced CVD (PECVD) and high density plasma CVD (HDP-CVD), to deposit material layers. In particular, the depositing of oxide insulating layers, also referred to as inter-metal dielectric (IMD) layers, is performed several times in the formation of a multi-level integrated circuit device.
Generally, the formation of IC devices involves a major effort in forming multiple levels of wiring, also referred to as damascene structures, which are formed by backfilling metals, for example copper, into openings etched into IMD layers.
Increasingly, low-K (dielectric constant) IMD layers are required to reduce signal delay and power loss effects as IC devices are scaled down in size. One way this has been accomplished has been to introduce porosity or dopants into a silicon oxide dielectric insulating layer, also referred to as an inter-metal dielectric (IMD) layer. Increasingly, low-K silicon oxide based materials are formed using organo-silane precursors in a PECVD or HDP-CVD process to form porous organo-silicate glass (OSG) IMD layers having dielectric constants less than about 3.2.
One problem with PECVD and HDP-CVD processes is the formation of coatings of IMD layer deposition material over surfaces within the plasma reactor. The formation of residual deposition material becomes a problem in subsequent CVD depositions in several respects including flaking off of the residual deposition material onto the process wafer during a PECVD deposition process thereby introducing defects into a newly deposited CVD layer, for example an IMD layer. In addition, the presence of dopants, such as fluorine in prior art processes has tended to cause problems in subsequent depositions of non-doped IMD layers by undesirably introducing fluorine contaminants due to interaction of the deposition plasma with the residual deposition material within the chamber.
The most obvious and reliable solution to the problems presented by residual deposition materials in a plasma reactor chamber is to perform preventative maintenance, or cleaning of the plasma reactor chamber on a frequent basis. However, the down time of the plasma reactor chamber and the labor intensive requirements for manual preventative maintenance functions increases the cost of manufacture proportionate to the frequency of such required maintenance. Several approaches in the prior art have sought to alleviate the cost of preventative maintenance by depositing protective coatings over the accumulated coatings at periodic times to reduce interaction of the residual deposited material with the plasma and extend the preventative maintenance life-cycle. Unfortunately this approach makes the cleaning processes more difficult as the protective coatings are generally more resistant to cleaning processes, including plasma cleaning processes, requiring the use of fluorocarbons for effective cleaning.
For example, in plasma cleaning processes of the prior art fluorine containing gases, including fluorocarbons and hydrofluorocarbons, are used to form a plasma in a plasma cleaning process to remove residual deposition material by periodically etching away a portion of the accumulated coating material. This approach has its own drawbacks, including the cost of the fluorine containing cleaning gases, both in terms of manufacturing cost and environmental cost, and incomplete cleaning of the residual deposition material. For example, the use of fluorocarbons are generally discouraged and an increasing number are, or will be, subject to regulation limiting their use due to detrimental environmental effects, for example, associated with global warming effects as well as deterioration of the UV protective ozone layer of Earth's atmosphere.
Although prior art plasma reactor chamber cleaning processes have included the use of alternative fluorine containing gases, the cost of such gases remains significant, and fluorocarbons are still generally used to achieve more complete cleaning of the residual deposition materials. Additional problems related to the use of fluorine containing gases in a plasma cleaning operation includes undesired reaction of fluorine radicals with residual deposition material which can operate to reduce the effectiveness of the cleaning operation and contribute to subsequent non-uniform CVD layer deposition and particulate contamination.
There is therefore a need in the integrated circuit manufacturing art to develop a plasma cleaning process for plasma enhanced CVD reactor chambers whereby residual deposition material is more effectively removed to increase a subsequent CVD deposited film uniformity while reducing manufacturing and environmental costs.
It is therefore among the objects of the present invention to provide a plasma cleaning process for plasma enhanced CVD reactor chambers whereby residual deposition material is more effectively removed to increase a subsequent CVD deposited film uniformity while reducing manufacturing and environmental costs, in addition to overcoming other shortcomings of the prior art.